Merge branch 'mk-julia6' into 'develop'

julia 6

See merge request R3/school/courses!172

2023/2023-03-23_ProgrammingWithJulia-6/slides/6a-types.md

+
+<div class=leader>
+<i class="twa twa-locomotive"></i>
+<i class="twa twa-helicopter"></i>
+<i class="twa twa-police-car"></i>
+<i class="twa twa-trolleybus"></i>
+<br>
+Data and their types
+</div>
+
+
+
+# What are types?
+
+Types are a small domain-specific metalanguage that allows programs to *prove facts* about other programs
+
+- originally from set theory (after Russel's disaster, preceding the Gödel's disaster)
+- the classes of provable facts vary:
+  - in λ-calculi, types are theorems that often uniquely determine code
+  - in <i class="twa twa-snake"></i>, types are more like comments that do not prove anything
+  - in many languages, types determine the format of data interfaces and data
+
+
+Julia types:
+- determine the format of data
+- may carry additional information!
+- may be materialized ("reified") and used at runtime
+
+
+
+# Types in Julia
+
+Primitive types: `Int32`, `UInt64`, `Float32`, `Char`, `Nothing`, `Function`, ...
+
+Compound types:
+```julia
+struct FloatComplex
+  re::Float64
+  im::Float64
+end
+```
+
+
+
+# Types in Julia
+
+Parametrized types: `Tuple{...}`, `Array{...}`, `NTuple{N, ...}`, ...
+
+Type aliases:
+```julia
+const Vector{X} = Array{X, 1}
+```
+
+Abstract types (organized with `<:`):
+```julia
+abstract type Anything end
+struct Something <: Anything
+  ...
+end
+```
+
+`Union` and `UnionAll` types:
+```julia
+const Maybe{X} = Union{Nothing, X}
+const VectorOfReals = (Vector{T} where {T<:Real})
+```
+
+
+
+# How does dispatch work?
+
+Upon a function call, Julia selects the *least generic* method of the function
+- the ordering is defined by `<:` on parameter types
+- dispatch on multiple parameters is possible and (quite) efficient
+  - this is the main difference from many other languages!
+- dispatch on multiple parameters may be ambiguous!
+
+```julia
+julia> f(::Real, ::Int) = 1
+f (generic function with 1 method)
+
+julia> f(::Int, ::Real) = 2
+f (generic function with 2 methods)
+
+julia> f(1,2)
+ERROR: MethodError: f(::Int64, ::Int64) is ambiguous.
+```
+
+
+
+# How does dispatch work?
+
+Upon a function call, Julia selects the *least generic* method of the function.
+- the call is specialized
+- size of primitive types MAY be known (their data may be placed directly into registers or arrays)
+- size of abstract types may NOT be known (their data must be *boxed*)
+
+Compare:
+- `sizeof(['a','b'])`, `sizeof([1.1f0, 2.2f0])`, `sizeof([1.1f0, 'b'])`
+- function specialization possibilities:
+  - `function f(x::Any)`
+  - `function f(x::Int)`
+  - `function f(x)`, which is internally `function f(x::T) where {T}`
+
+
+
+# Exercise: let's make a ZOO
+
+Zoo has:
+- <i class="twa twa-elephant"></i> (with a numeric weight)
+- <i class="twa twa-penguin"></i> (each with a name)
+- <i class="twa twa-lion"></i> (each of which may be hungry or not)
+
+These are hierarchically organized:
+- there may be <i class="twa twa-soft-ice-cream"></i> stands
+- some things are grouped at the same place
+- there may be signposted <i class="twa twa-information"></i><i class="twa twa-up-right-arrow"></i> paths that lead to a farther thing
+- some things are placed in <i class="twa twa-construction"></i>enclosures<i class="twa twa-construction"></i>
+
+"You arrive at the zoo. There's a satiated lion and a small elephant, and also a signpost saying `penguins this way`. If you go that way, there are 5 penguins in an enclosure and an ice cream stand."
+
+
+
+# Exercises: ZOO
+
+Make functions that:
+- count all penguins
+- compute the weight of everything in the zoo
+- make all animals in the zoo do their typical sound (`nudge(myZoo)`)
+- find the most hidden animals in the zoo (they are behind the most signs)
+- find all paths to hungry lions that are not in an enclosure
+- print out a text description of the zoo
+- convert a Julia datatype to your custom zoo datatype
+  - `(:penguin, "El Jefe")`, `:hungry_lion`, `:satiated_lion`, `(:elephant, 50.0)`, `:ice_cream_stand`
+  - groups of things are in a vector
+  - signposted paths are made of Pairs (`"Penguins go here" => [(:penguin, ...), ....]`)
+  - `throw` a good error if some data cannot be processed

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2023/2023-03-23_ProgrammingWithJulia-6/slides/index.md

+
+# Programming with Julia
+
+## March 2023
+
+<div style="top: 6em; left: 0%; position: absolute;">
+    <img src="theme/img/lcsb_bg.png">
+</div>
+
+<div style="top: 1em; left: 60%; position: absolute;">
+    <img src="slides/img/julia.svg" height="200px">
+    <h1 style="margin-top:3ex; margin-bottom:3ex;">6: Types and dispatch</h1>
+    <h4>
+        Miroslav Kratochvíl<br>
+        Laurent Heirendt<br>
+        LCSB, DSSE<br>
+    </h4>
+</div>
+
+<link rel="stylesheet" href="https://lcsb-biocore.github.io/icons-mirror/twemoji-amazing.css">
+<style>
+	code {border: 2pt dotted #f80; padding: .4ex; border-radius: .7ex; color:#444; }
+	.reveal pre code {border: 0; font-size: 18pt; line-height:27pt;}
+	em {color: #e02;}
+	li {margin-bottom: 1ex;}
+	div.leader {font-size:400%; line-height:120%; font-weight:bold; margin: 1em;}
+	section {padding-bottom: 10em;}
+</style>

2023/2023-03-23_ProgrammingWithJulia-6/slides/list.json

+[
+    { "filename": "index.md" },
+    { "filename": "6a-types.md" }
+]